This invention relates to a vessel for transport of a floating buoyant cargo, such as barges, lighters and pontoons.
A previous application, Ser. No. 511,492, now U.S. Pat. No. 3,913,512, Oct. 2, 1974, describes a vessel of this general type, and the present invention may be considered as an improvement over that invention. In that invention, the hold of the vessel is always open to the ocean waters. While such a vessel is quite feasible, the hold can be pumped dry for maintenance and repair work only by first placing the vessel in a dry dock.
The previous application shows a vessel with openings going directly through the bottom shell of the hull, and such openings create hydrodynamic drag which can slow the speed of the vessel on the ocean.
An important purpose of the present invention is to provide a vessel obtaining the desirable features of operation of the preceding invention, wherein advantage is taken of the buoyancy of the cargo to help support the ship, while at the same time making it possible to dry out the hold for, e.g., maintenance, cleaning or painting, when the ship is empty of cargo, without having to place the ship in dry dock.
It is also an object of the present invention to provide for the free exchange of water between the ocean and the hold during the voyage where the cargo is being carried, and also to make it possible to keep the hold readily flooded at all times, except when the vessel is to be pumped dry.
Another object of the invention is to provide a vessel of the type in which the cargo is buoyantly supported during the voyage by ocean water, while at the same time providing an imperforate hull giving a better hydrodynamic surface for movement through the water. In other words, instead of a hull that has openings directly in its bottom shell that tend to create resistance in the water, the present invention is adapted to provide a more usual type of hull while still fully realizing the advantages of the flooded hold.